Control for air quality machine

ABSTRACT

A multi-functional room air conditioning unit that controls both heat and humidity as well as the concentration of airborne particulates. A control unit monitors temperature, humidity and air quality parameters and automatically programs the apparatus to take corrective action when one or more of the parameters is outside of the desired range.

BACKGROUND OF THE INVENTION

This invention relates to the real-time monitoring and control of airquality in a work or living space, and is more particularly concernedwith devices that provide a measurement of health quality andcontaminant concentration levels of ambient air. The invention is alsoconcerned with control devices for controlling operation of airtreatment and removal of particulates in connection with a room airhealth and comfort unit.

In order to provide satisfactory air quality in an environmental workspace or living space, it is desirable to obtain an indication of thecontaminant concentrations in the space, both in terms of gas or vaporconcentrations (i.e., CO, SO₂ or other noxious gases), or airborneparticulate concentrations, (i.e., dust, aerosol droplets, bacteria,spores, pollen, and viruses). Then it is necessary to compare themeasured values with threshold limit values (TLVs) which correspond tothe levels of contaminant concentration to which humans can becontinuously exposed without significant adverse health risk. Levelshigher than TLVs represent air quality that is marginal to unacceptable.

In the United States, threshold limit values are established bygovernment agencies such as the National Institute of OccupationalSafety and Health (NIOSH) and the Occupational Safety and Health Agency(OSHA) based on information compiled by the American Conference ofGovernmental and Industrial Hygienists (ACGIH) with additional publisheddata from the Environmental Protection Agency (EPA), and standards fromthe American Society of Heating, Refrigeration and Air ConditioningEngineers.

However, measurement of air quality has required special, complexequipment to be used by specially trained personnel. It was not possiblefor a lay person to obtain a real-time reading of air quality in anenvironmental work or living space. In addition, there has not been anysuitable combined control circuitry available for controlling room airquality equipment, for controlling comfort factors, such as heat andrelative humidity, as well as health factors such as particulate and gasconcentrations to remain below their respective TLVs. There has been nocontrol circuit provided for environment control equipment to monitorand control air quality based on temperature, relative humidity,particulates and aerosols concentration or gas concentration levels.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, it is an object of this invention to provide accuratereal-time sensing and display of environmental air quality (NIAindication of humidity, temperature, and contaminant level).

It is another object to provide an environmental air quality measuringdevice which can monitor air quality parameters and display same in realtime.

It is a further object to provide control of a room air health andcomfort unit to maintain temperature and relative humidity withindesired limits and to maintain particulate and gas concentrations belowpredetermined TLVs.

According to an aspect of this invention a portable electronicmonitoring device senses and indicates air quality within a given space.Within its housing the device has a particulate sensor for detecting theambient concentration of aerosols and particulates in the space and forcomparing the detected level with a predetermined particulates TLV. Agas sensor in the housing detects the ambient concentration level of oneor more predetermined gases, such as CO, CH₄, SO₂, etc., and comparesthe same with a predetermined gas TLV. A temperature sensor measures theambient temperature in the environmental space; a humidity sensor in thehousing detects ambient relative humidity in the environmental air inthe vicinity of the device. There is a particulate display on a panel ofthe housing, and the display can be in the form of a row of LEDs withone LED indicating a satisfactory air quality when the detectedparticulate level is within the acceptable TLV based upon establishedstandards. A similar row of LEDs or equivalent display indicatesacceptable gas concentration when the target gas or gases have aconcentration below the gas TLV. When the gas or particulate level isdetected above the TLV another LED illuminates to indicate that the airquality has become marginal or unacceptable. There are also displays,such as liquid crystal displays, to indicate the temperature andrelative humidity of the air in the vicinity of the device. These can beseparate or a combined dual-function display. The control circuit forsampling the various sensors and actuating the displays assumes a lowpower standby mode when the sensors indicate that the particulates andgas concentrations are below the respective TLVs, and the humidity andtemperature are within their target comfort ranges. If any of thesedetected parameters rises (or falls) to an abnormal level, e.g. if theparticulate concentration level reads higher than the particulate TLV,then the control circuit automatically switches over to a highsensitivity mode. In the low sensitivity mode the control circuitsamples the sensors at a low rate; this conserves battery power and alsolimits false readings of excessive gas or particulate concentration.When the control circuit switches to the high sensitivity mode, thesensors are sampled more frequently. However, in this mode a repetitionof high readings for three or more samples is required to produce an"unacceptable" display on the gas or particulate concentration display.Also three or more successive high readings of gas or particulate arerequired for the control circuit to actuate an alarm. The alarm can be aflashing LED if the gas or particulates concentration is just above theTLV (indicating marginal air quality) or a sounder or buzzer if the gasor particulates concentration is well above the TLV (indicatingpotentially health-threatening air quality).

The device can be portable or placed in a permanent location in a roomwhere air quality should be monitored. Because of the low powerrequirements, the device can be left on continuously.

The same control circuit can also be employed to control a room airhealth and comfort air quality machine which can provide airpurification (both of particulates and of one or more gases),temperature control (heating, cooling or both), and humidity control(humidification or dehumidification). The unit housing has an air inletto admit room air into an air pathway. The air passes through mechanicalprefilter media for collection of larger airborne contaminants, thenthrough an ionization section and electrostatic charged grid, mesh, ormedia for removal of microscopic particulates from the air stream.Organic compounds are removed from the air stream. Organic compounds areremoved from the air stream through the use of radiant energy sources,and/or adsorptive, absorptive or catalytic media filters, such asactivated carbon, silica gel, or alumina to remove gaseous contaminantssuch as SO₂, CO₂, O₃ and/or other gases. Each of the aforementionedfilter systems can be used independently or in any combination in themachine. A blower then moves the air past heat control elements, e.g. anevaporator heat exchange coil to cool and dehumidify the air and/or aheating coil to heat the air, as required. After this a humidifier,either a web of porous mesh or other material in contact with water in areservoir, or an ultrasonic humidification process can be actuated toadd water vapor to the air stream as required. In a favorableembodiment, the unit is free-standing and can be wheeled into a roomwhere air comfort and quality needs to be controlled closely. However,in other embodiments it can be a permanent installation serving a roomor suite of rooms.

As in the measuring unit discussed previously, in this embodiment thereare temperature and humidity sensors plus particulate and gas sensors.There are also temperature and humidity setpoint selectors, andparticulate and gas concentration displays. These are preferably each aseries of LEDs disposed on a front panel of the unit. The controlcircuit operates the blower or fan, heater, air conditioner compressor,humidifier, and dehumidifier, as required, based on outputs of thetemperature and humidity sensors as compared with high and lowtemperature setpoints and a relative humidity setpoint. The blower speedcan be increased when the particulate concentration is high.

The control circuit assumes a low-sensitivity mode when the sensors allindicate normal levels of the measured parameters, and if theparticulate or gas concentration or the temperature reaches an abnormallevel (i.e., below a heating setpoint or above an air conditioningsetpoint), the control circuit automatically switches over to ahigh-sensitivity mode, as described before in connection with themonitoring device.

Pressure differential can also be detected, and if this becomesabnormal, an indicator will signal that various system filters should bechanged or cleaned.

The above and many other objects, features, and advantages of thisinvention will present themselves to those skilled in the art from theensuing description of selected preferred embodiments, to be read inconjunction with the accompanying Drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a sectional side elevation of a room air health and comfortmachine according to one preferred embodiment of this invention.

FIG. 2 is a front elevation of the unit of FIG. 1, showing at 1--1 theviewing direction of FIG. 1.

FIG. 3 is a schematic view of the sensors, displays, and controlcircuitry of this invention.

FIG. 4 is a top plan view of a hand-held monitoring unit according toanother embodiment of this invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The pathway of air through an air health and comfort unit should haveelements to perform the various air handling, purification and treatmentfunctions, for example, as follows:

1. Mechanical pre-filter media devices to filter the larger aircontaminants out of the air stream.

2. Ionizing section with high voltage section to ionize the gasmolecules in the air stream thus producing charges which attachthemselves to air contaminants.

3. Collecting section, i.e. high voltage alternately-charged section ofgrid mesh or media to collect the microscopic airborne contaminants.

4. Radiant energy section, e.g., high-and low-frequency radiant energysources to remove airborne organic compounds.

5. After-filter section where chemisorb media filters utilizeadsorption, absorption or catalytic means to remove volatile organiccompounds from the air stream.

6. Humidification section, designed to add water vapor, as needed, tothe air stream.

7. Air handler system for drawing air into the unit and exhausting itback into the room environment.

8. Heater section designed to add or heat energy as needed to the airstream.

9. Cooling section designed to cool the air stream, as needed.

10. Dehumidification section designed to remove water vapor from the airstream, as necessary.

With reference to the Drawing, and initially to FIGS. 1 and 2, afree-standing air conditioning and air purification unit 10 has a shellor housing 12. Intake air from the room, work space, or living space,passes into the unit through a back grill 14 and thence through a coarsefilter or prefilter 16 into an electrostatic air purifier 18.Preferably, the air purifier 18 is of the charged-grid type, to whichhigh voltage is supplied from a power supply 20. Air proceeds along itspathway through the unit 10 passing through a gas-adsorptive filter 22.This filter 22 employs active carbon, silica gel, or another adsorptiveor absorptive medium. A blower 24 positioned after the filter 22 movesthe air through the unit 10. Here, the blower 24 is of the cross-flowtype having a vertical axis and a motor 26 at one end. In otherembodiments, one or more propeller fans could be used instead. Theblower 24 forces air through a cooling coil 28, for example, anevaporator coil of an air conditioning system, of which a compressor 30is shown. A condenser coil would also be associated with the coolingcoil 28 and compressor 30, but is not shown in this drawing.

A set of heater coils 32 is positioned after the cooling coil 28.Preferably, these are electric coils of a high-efficiency resistiveheating design. A humidifier 34 follows the heater coils 32, and can beformed of a continuous web 36 of a rather porous mesh which whenactuated, travels between a water reservoir 40 and air in the pathway,which passes from there through a front grill 42, where the conditionedair is discharged back into the room. A separate reservoir 40 can alsobe employed for catching condensed water from the cooling coil 28 whenthe unit 10 is in a cooling mode. A control circuit 44, here shown inFIG. 1, controls the operation of the various parts of this unit 10, inaccordance with ambient conditions, as compared to predetermined orselected setpoints.

As shown in FIG. 2, there are various control knobs and indicators on afront panel of the housing 12. These are coupled to the control circuit44. There is a bar-type LED particulates concentration indicator 46 anda similar LED gas concentration indicator 48, and there are also adigital display of relative humidity 50 and a digital display of ambienttemperature 52. Both of these are preferably liquid crystal displays,but other visual display means could be employed. In other embodiments asingle display can show humidity and temperature alternately.

An on/off, high/low fan speed switch 54 is provided on the front of theunit 10, as are setpoint adjustments including an adjustment knob 56 forparticulates concentration sensitivity, a knob 58 for gas concentrationsensitivity, a knob 60 for adjusting the relative humidity setpoint, andanother knob 62 for adjusting the temperature setpoint or setpoints. Onthe lower part of the front of the housing there is a visible waterreservoir level indicator 64 to indicate the amount of water containedin the reservoir 40. Also shown in FIG. 2 is an exhaust air conduit 66,for conducting out of the room another stream of air which passes overthe not-shown condenser coil to conduct heat to outside of the livingspace or workspace.

In this embodiment, the control circuit 44 includes a digital controlcontaining a microprogram which controls the speed of the blower 24 as afunction of particulates concentration or gas concentration level. Thatis, the blower speed increases if the detected level is higher than apredetermined threshold level value (TLV). Other functions are alsopossible to be controlled by microprogramming, i.e., for controlling theoperation of the compressor 30, the heater coils 32, or the humidifier34 as a function of temperature and relative humidity. Such programs arewell known.

FIG. 3 is a schematic circuit diagram of one form of the control circuit44 according to this invention. Here are shown the particulatesconcentration level setpoint selector 46, the gas concentration setpointselector 48, relative humidity setpoint selector 50, and temperaturesetpoint selector 52. At the heart of the circuit 44 is a microprocessorintegrated circuit chip 68 with a number of inputs (shown on the righthand side) as well as outputs (on the left hand side) used to controlheat, air conditioning, humidity, and fan speed, and to actuate a numberof displays.

A particulate sensor 70 senses the concentration of particulates in theambient air in the vicinity of the unit 10, and supplies a particulatelevel signal to a comparator 72 which compares that level with asetpoint provided from the selector 46. In this case, the comparatorprovides a number of outputs, for example, indicating "good" oracceptable air quality when the detected particulates level is below theestablished TLV, a "bad" or unacceptable signal when the particulateslevel is above the particulate TLV, and one or more marginal or "fair"signals when the particulate level is near the TLV.

A gas sensor 74 detects the level of concentration of one or moreundesirable gases in the ambient air. These gases, for example, couldinclude carbon monoxide, sulfur dioxide, methane, or other toxic orhealth-threatening vapors. The gas sensor 74 provides an output levelwhich is fed to a comparator 76. This comparator is also provided with asetpoint from the setpoint selector 58, and thus provides a "good"indication, an "unacceptable" indication, and one or more intermediateindications, depending on the value of the detected gas concentrationrelative to the gas TLV.

A relative humidity sensor 78 provides a relative humidity level to acomparator 80 which is also coupled to the relative humidity setpointselector 60. The relative humidity level is also fed to the relativehumidity display where it is decoded and displayed in digital form.

A temperature sensor 84 senses the temperature of the air in thevicinity of the unit 10, and supplies a temperature value to acomparator 86 which is also coupled to the temperature setpoint selector60. The temperature value is also fed to the temperature display 52,where it is decoded and displayed in digital form.

An alarm 90, which can be an audible or visible alarm, is actuated ifthe particulate concentration is detected to be at an unacceptablelevel.

There is also a pressure differential detector 94 disposed along thepathway of air within the unit 10, for sensing pressure differential,for example, across the gas absorbent filter 22. A pressure differentialsignal is fed from the detector 94 to a comparator 96 which provides asignal along a high channel or "normal" channel depending on the valueof the pressure differential.

If the pressure is too high, the microprocessor chip 68 will light achange-filter display 98, to indicate that the gas filter 22 should bechanged out.

One set of outputs from the microprocessor chip 68 supplies inputs ofthe particulates LED indicator 46 which, as aforementioned, includes anLED indicator which lights if the particulates level is satisfactory,and one or more additional LED indicators which light when theparticulates level is less than satisfactory. This indicator 46 can alsoinclude the visual or audible alarm 90 which is actuated when theparticulates sensor 70 detects that the particulates level is well abovethe particulates TLV.

In similar fashion, a number of the outputs of the microprocessor chip68 are connected to inputs of the gas sensor display or indicator 48, inwhich include an LED indicator which lights when the detected gasconcentration level is below the gas TLV, as well as one or moreadditional LED indicators which light when the gas level is at anunsatisfactory or unsafe level, that is, near or below the gas TLV.Also, the audible or visual alarm can be actuated when the gas sensor 74detects that the gas in question has a concentration above theappropriate L.E.L. or TLV. The microprocessor chip 68 is suitablyprogrammed to assume a low-sensitivity active mode, i.e. a standby mode,when the detected temperature and humidity are within normal bounds,that is, if the humidity is above a "dry" level, such as 45% R.H., andif the temperature is above the temperature for which heat is requiredyet below the temperature for which cooling is required, and also wherethe particulates and gas concentrations are below the respectivethreshold limit values. In other cases, the microprocessor chip 68 isoperative to switch over to a high sensitivity mode, that is, wheneither heating or cooling is called for, or if moisture must be added tobring the relative humidity up to an acceptable level. Themicroprocessor chip 68 also automatically switches over to a highsensitivity mode when the detected particulate concentration is abovethe particulate TLV or when the gas concentration is above the gas TLV.If all of these levels, to wit, temperature, relative humidity, gasconcentration and particulate concentration are returned to a normallevel, the chip 68 remains in the high-sensitivity mode for apredetermined interval, and then returns to the low-sensitivity mode. Onthe other hand, to prevent spurious or intermittent signals fromactuating the circuit 44, a predetermined number of consecutive timesamples of particulates level, gas level, relative humidity, and/ortemperature, are required to be abnormal before the high-sensitivitymode is selected.

When in the low-sensitivity mode, the microprocessor chip 68 isoperative to sample its respective inputs of particulate, gas, relativehumidity, and temperature at a relatively low rate. However, in thehigh-sensitivity mode, the chip 68 is operative to sample theparticulate level, the gas level, the temperature level, and therelative humidity level at relatively high rate. The blower speed canthen be automatically increased if additional particulate removal or gasremoval is called for. If heating or cooling is called for, themicrochip 68 is operative to automatically actuate the compressor 30 orthe heater coils 32, as appropriate. If the humidity level is detectedto be too low, the humidifier 34 is automatically actuated. Thus, theair conditioning and air purification unit 10 automatically controls theair quality in the workspace or living space to provide a healthy andcomfortable work and living environment, and at the same time indicatesthe comfort level, as well as the healthiness of the air, in terms ofparticulate level, gas concentration level, temperature, and relativehumidity.

As shown in FIG. 4, an air quality indicator 100 is provided as ahand-held or wall-mounted instrument for measuring and indicating theelements of air quality which have been described in connection with theembodiment of FIG. 1. Here there is a housing or shell 110 with openings112 to admit air to relative humidity and temperature sensor within theinstrument, as well as further openings 114 to admit air in the vicinityof the instrument to a particulate sensor and a gas sensor. On the frontof the instrument there are provided an LCD temperature display 116, anda LCD relative humidity display 118. The temperature can be provided indegrees F. or degrees C., while relative humidity is provided, as isconventional, in percent.

An LED particulate concentration indicator 120 is provided as a bar-typeindicator having a green LED 120a which lights when the particulateslevel is below the particulate TLV, two yellow LEDs 120b and 120c whichlight when the detected particulates level is between the high and lowparticulate TLV, thus indicating fair or poor air quality, and a red LED120d which lights when the detected particulate concentration is abovethe TLV, thus indicating an unacceptable or dangerous particulateconcentration.

A second LED indicator 122 is employed for indicating the concentrationof a gas or vapor, such as carbon monoxide. Here, as in the particulatesindicator, this indicator 122 has a green LED 122a which lights when thegas concentration is below the gas TLV, first and second yellow LEDs122b, 122c which light when the detected gas concentration is betweenthe high and low gas TLV thus indicating fair or poor air quality, and ared LED 122d, which lights when the detected gas concentration is abovethe predetermined gas TLV, thus indicating an unacceptable or dangerousconcentration of gases. The circuit as generally shown in FIG. 3 is alsoemployed in the detector instrument 100 of this embodiment andautomatically assumes a low-sensitivity mode when the gas andparticulates levels as detected are below their respective thresholdlimit values or TLVs. In the low sensitivity mode, as mentionedpreviously, the sampling of the particulate, gas, humidity, andtemperature sensors is carried out at a low sampling rate. This permitsthe instrument 100 to operate at a low power drain. However, if theparticulate level or the gas concentration level moves into a fair,poor, or unacceptable level, and this is sustained for more than somepredetermined number of time samples, the control circuit 44 willautomatically assume a high-sensitivity mode, wherein the sampling ofthe sensors is carried out in an increased frequency.

In the low-sensitivity mode the green indicating LED's 120a and 122a arelit, showing a good condition for both gas concentrations andparticulate concentrations. This condition allows the instrument tooperate in a low power draw. An audible alarm can be included toindicate a dangerous level of particulate or gas concentration.

The instrument 100 of FIG. 4 can be hand held to permit a worker to testair quality in various rooms by carrying the device from room to room.However, the same device can also be wall mounted and left within a roomto indicate the air quality. In this case, a low-battery-chargeindicator can also be incorporated. This feature is not shown, but manylow-battery indicators are well know.

The instrument 100 can also be installed on a horizontal surface, suchas a desk or table.

The gas sensor is a semi-conductor solid-state detector, utilizingtin-oxide material, although there are many other gas detectors on themarket. For particulate detecting, an ionization detector or backscattering IR detector can be employed. The effects of relative humidityon particulate measurement are canceled out by the microprocessor chip.

Further, while the air conditioning and air purification unit 10 of FIG.1 and 2 has selectable set points for the particulates, gas, relativehumidity, and temperature levels, it should be understood that any orall of these parameters could be factory preset. The unit 10 could beconstructed without the air conditioning capability, and would stillfall within the main principles of the present invention.

While this invention has been described in detail with reference tocertain preferred embodiments, it should be understood that theinvention is not limited to those precise embodiments; rather, manymodifications and variations would present themselves to those of skillin the art without departing from the scope and spirit of thisinvention, as defined in the appended claims.

What is claimed is:
 1. A room air health and comfort unit forconditioning air in a room to control heat and humidity and also tocontrol the concentration of airborne particulate and one or more gasesin the air, comprisinga housing; an air inlet to admit room air into anair pathway in the housing; air purification means in said pathway toremove said particulate and said one or more gases from the room air; ablower after said air purification means to force air through saidpathway; heat adjustment means after said blower for adjustingtemperature of the air in the pathway; humidifier/dehumidifier meansafter said heat adjustment means for adding or removing moisture asnecessary to or from the air in the pathway; air outlet means forreturning the treated air from the air pathway into the room; andcontroller means for controlling operation of said unit includingparticulate sensor means for detecting ambient concentration of aerosolsand particulate in said room air, comparing same with a predeterminedparticulate threshold limit value, and providing a particulate sensoroutput; gas sensor means for detecting ambient concentration of said oneor more gases, comparing same with a gas concentration threshold limitvalue, and providing a gas sensor output; temperature sensor means forsensing ambient temperatures of the room air in the vicinity of the unitand providing a temperature output; humidity sensor means for detectingambient relative humidity of the room air in the vicinity of the unitand providing a relative humidity output; means providing at least oneroom air temperature setpoint; means providing a room air relativehumidity setpoint; particulate display means on a panel of said housingfor providing a "satisfactory" indication when the ambient concentrationdetected by said particulate sensor means is below said threshold limitbut providing at least one "unsatisfactory" indication when the detectedambient concentration is above said threshold limit; gas concentrationdisplay means on an outer panel of said housing for providing a"satisfactory" indication when the detected ambient concentration ofsaid one or more gases is below said gas concentration threshold limitvalue but providing at least one "unsatisfactory" indication when saidambient concentration is above said gas concentration threshold limitvalue; and control circuit means within said housing and having inputscoupled to said particulate sensor means, said gas sensor means, saidtemperature sensor means said humidity sensor means, said temperaturesetpoint means and said relative humidity setpoint means, and outputsconnected to said heat adjustment means, said humidifier/dehumidifiermeans, said particulate display means, said gas display means, and saidblower; and operative to control operation of said heat adjustmentmeans, said humidifier/dehumidifier means and said blower based on saidparticulate sensor output, said gas sensor output, said temperatureoutput, said relative humidity output, said temperature setpoint andsaid relative humidity setpoint; said control circuit means assuming alow-sensitivity active mode when said detected temperature and humidityare on normal sides of their respective setpoints and when said detectedparticulate and gas concentrations are respectively below saidparticulate and gas concentration threshold limit values, but beingoperative automatically to switch over to a high-sensitivity mode whensaid temperature is on an abnormal side of the temperature setpoint,said relative humidity is on an abnormal side of the relative humiditysetpoint, said detected particulate concentration is above its thresholdlimit value or said gas concentration is above its threshold limitvalue, the control circuit being operative in said low-sensitivity modeto sample said particulate sensor output, said gas sensor output, saidtemperature and said relative humidity at a low rate and in said highsensitivity mode to sample said particulate sensor output, said gassensor output, said temperature and said relative humidity at arelatively high rate.
 2. A room air health and comfort unit according toclaim 1, wherein when said control circuit means automatically switchesto its high-sensitivity mode, the control circuit means is operative tosample each of said particulate sensor output, said gas sensor output,said temperature and said relative humidity a predetermined number ofsamples in succession, and is operative to actuate said blower, saidheat adjustment means, said humidifier means, said particulateconcentration display means "unsatisfactory" indication only if arespective one of said particulate concentration or said gasconcentration remains above its respective threshold limit value, orsaid temperature or said relative humidity remains on an abnormal sideof its respective setpoint for at least said predetermined number ofsamples.
 3. A room air health and comfort unit according to claim 2,wherein when said temperature and humidity return to the normal side oftheir respective setpoints and said particulate concentration and gasconcentration fall below their respective threshold limit values whensaid control circuit means is in its high-sensitivity mode, the controlcircuit means is operative to remain in its high-sensitivity mode for apredetermined time period and then automatically to return to its saidlow-sensitivity mode if the temperature and humidity remain on thenormal side of their setpoints and if the particulate concentration andgas concentration remain below the threshold limit and threshold limitvalue, respectively.
 4. A room air health and comfort unit according toclaim 1 further comprising pressure differential detector means fordetecting a pressure drop between two points in said air pathway, and analarm providing an alarm signal if said pressure drop rises to apredetermined abnormal level.
 5. A room air health and comfort unitaccording to claim 1 wherein said air purification means includesionizer charged-grid type electrostatic filter followed by agas-absorptive media filter.
 6. A room air health and comfort unitaccording to claim 1 wherein said air purification means includesmechanical media filter followed by a gas-chemisorptive media filter. 7.A room air health and comfort unit according to claim 1 wherein saidheat adjustment means includes an evaporator heat exchanger coil forremoving heat from air in the pathway, and a heating coil for addingheat the air in the pathway.